GD&T Geometric Symbols & Notation 5 — Questions and Answers
Question 1: What does the continuous feature symbol (CF) indicate in a GD&T callout?
- Multiple interrupted features are treated as a single continuous feature (Correct answer)
- The tolerance applies continuously along the full length
- The feature must be machined without interruption
- The tolerance is applied to continuous production runs
Correct answer: Multiple interrupted features are treated as a single continuous feature
The CF (Continuous Feature) symbol specifies that two or more interrupted features of size are treated as a single unified feature for measurement purposes.
Question 2: In a feature control frame using the ASME Y14.5 standard, how many datum references can be specified?
- Up to three (primary, secondary, tertiary) (Correct answer)
- Only one
- Up to two
- Unlimited
Correct answer: Up to three (primary, secondary, tertiary)
A feature control frame can reference up to three datums (primary, secondary, tertiary) to fully constrain the six degrees of freedom.
Question 3: A 'unilateral profile' tolerance where the band is entirely inside the true profile is indicated by:
- A 'U' symbol with the inward offset value specified (Correct answer)
- A minus sign before the tolerance
- An arrow pointing inward on the feature
- Two separate tolerance values with a slash
Correct answer: A 'U' symbol with the inward offset value specified
In ASME Y14.5-2009 and later, an unequal/unilateral profile tolerance is shown with the 'U' symbol and a value indicating how much of the tolerance is on one side.
Question 4: Which GD&T characteristic is the only one that can control all six degrees of freedom simultaneously?
- True Position
- Profile of a Surface (Correct answer)
- Flatness
- Total Runout
Correct answer: Profile of a Surface
Profile of a Surface with appropriate datum references can simultaneously control size, form, orientation, and location — all six degrees of freedom.
Question 5: A 'non-rigid part' notation on a drawing indicates:
- The part must be inspected in a restrained or free state as specified (Correct answer)
- The part has flexible tolerances
- The part can deform during assembly
- The tolerances apply only to rigid sections
Correct answer: The part must be inspected in a restrained or free state as specified
Non-rigid part notation flags that the component may distort under its own weight or residual stresses, and the drawing specifies whether inspection is in free or restrained state.
Question 6: The symbol for 'Concentricity' in GD&T consists of:
- Two concentric circles (Correct answer)
- A circle with a center dot
- A single circle with crosshairs
- Two overlapping circles
Correct answer: Two concentric circles
Concentricity is represented by two concentric circles and controls that the median points of a diametrically opposed feature lie within a cylindrical tolerance zone coaxial with a datum axis.
Question 7: When a GD&T callout references 'Datum A' as primary, 'Datum B' as secondary, and 'Datum C' as tertiary, the order matters because:
- Each successive datum constrains additional degrees of freedom left open by the previous datum (Correct answer)
- The primary datum is always the most precise
- Tertiary datums override primary datums for location
- The order determines inspection sequence but not the tolerance zone
Correct answer: Each successive datum constrains additional degrees of freedom left open by the previous datum
The datum precedence order determines which datum stops which motions first; the primary datum constrains the most DOF, and each subsequent datum constrains remaining ones.
GD&T Geometric Symbols & Notation 5
What does the continuous feature symbol (CF) indicate in a GD&T callout?